Lithium disilicate

Figure 4-3 Experimental data on nucleation rate in lithium disilicate melt (points) compared to theory. The solid curve is a fit to the experimental data. The short dashed curve (middle curve) is the theoretically calculated curve multiplied by 1.7 xlO °. Parameters used in calculating the theoretical curve using Equation 4-9 Te=1306K, a O.ZOlJ/m, l c = 61.2cm /mol, AHm-c = 61.1 kj/mol, = (Neilson and Weinberg, 1979). The long...

Fuss T., Ray C.S., Lesher C.E., and Day D.E. (2006) In situ crystallization of lithium disilicate glass effort of pressure on crystal growth rate. /. Non-Cryst. Solids 352, 2073-2081. 

Neilson G.F. and Weinberg M.C. (1979) A test of classical nucleation theory crystal nu-cleation of lithium disilicate glass. /. Non-Cryst. Solids 34, 137-147. 

Corning 8603 lithium metasilicate, Li20Si02 lithium disilicate, Li20-2 Si02 photochemically machinable fluid amplifiers... 

Simple Silicates. The most important simple silicate glass-ceramics are based on lithium metasilicate [10102-24-6], Li SiO, lithium disilicate... 

In many cases, more than one crystalline phase forms. Often, phases that form initially transform into another phase as heat treatment progresses. For example, crystalline phases of /5-quartz solid solutions (e.g., (S-eucryptite), which are not stable at high temperatures, convert to more stable phases (e.g., 6-spodumene, cristobalite, sapphirine, or lithium disilicate). The stable high temperature phase may have different properties— in this case, higher thermal expansion. Therefore, glass ceramics with the same chemical composition may have very different properties, depending on the heat treatment. 

Li2Si205 LITHIUM DISILICATE 984 Mg2Si 2-MAGNESIUM SILICON 1029... 

Li P. 1995. Crystallization Behavior of Sol-Gel Derived Lithium Disilicate Powders and... 

Express the following compositions in stoichiometry formulae. (example-Li2Si205 for lithium disilicate) ... 

Glass-ceramics are also used for dental prosthetics. These materials are primarily based on either lithium disilicate or calcium phosphate glasses. Machinable glass-ceramics based on fluoromica phases have also been developed for machined inlays. All of these materials must be stained to match the surrounding teeth to be acceptable to the patient. 

The dental ceramics used in this study are described in Table I. Materials were selected in order to provide varied microstructures a) the glass-ceramic El is expected to have a homogeneous microstructure and isotropic properties b) the glass-ceramic E2 is expected to have anisotropic properties due to alignment of lithium disilicate fibers and c) the glass-infiltrated alumina composite IC, may have particle orientation, which could affect the mechanical properties. 

E2 Ivoclar Vivadent / IPS Empress 2 Heat-pressed, glass-ceramic with lithium disilicate, used as core material in crowns and bridges... 

Figure 1. SEM Images of polished surfaces ofi (a) leucite-based glass ceramic El, after etching in 10% HF solution (b) lithium disilicate-based glass ceramic E2 and (c) glass-infiltrated alumina composite IC. Note (a,c) - secondary electron image (SET) and (b) - backscattered electron im e (BEF).

Figure 2. XRD patterns of materials tested (a) leucite-based glass ceramic El (b) lithium disilicate-based glass ceramic E2 and (c) glass-infiltrated alumina composite 1C.

Figure S. Schematic representation of the alignment of needle-like lithium disilicate particles in glass-ceramic E2 for disc shaped specimen. Larger arrow indicates the direction of pressing and small arrows indicate the possible pressing force directions that resulted in particle aligmnent.

B6 3 unit posterior bridge Broke in vivo at 7 weeks 2011 IvoclarA ivadent e.max Press lithium disilicate Connector fracture from normal loading. Origin was a tiny contact damage site in the veneer. The connector was too small. 

CASE B6 Three-unit e.max Press lithium disilicate bridge... 

Figure 6.11 XRD spectrum of the crystallized glass-ceramic showing the presence of cristobalite, lithium metasilicate, lithium disilicate, and lithium orthophosphate phases.

Findings from the theories of nucleation have also contributed to the optimization of these comprehensive experimental investigations. As a result, glass-ceramics with improved properties have been produced, specifically glass-ceramics with specific solid-solution limits like j3-spodumene and stuffed P-quartz or with stoichiometric compositions like cordierite and lithium disilicate. Initial results for the successfU application of the theory of nucleation to multicomponent glass-ceramics with a nonstoichiometric composition were achieved with mica and anosovite glass-ceramics. 

Since 1959, however, the principle of heterogeneous nucleation with metals has been successfiilly applied in the development of only a few glass-ceramics. To produce lithium disilicate glass-ceramics, McCracken et al. 

As mentioned in the History section, lithium disilicate glass-ceramic was the first glass-ceramic that Stookey (1953, 1959) developed. The fimdamen-tal research conducted by Stookey provided a basis for the large-scale development of glass-ceramics in a variety of chemical systems. Furthermore, other materials systems based on lithium disilicate have been also developed according to his findings. 

The initial basis for the development of a material in the lithium disilicate system were compositions that were derived from the stoichiometric composition of phyllosilicate crystals, The structure is shown in Appendix... 

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